Coated lithium-rich lithium supplementing agent material, preparation method and application thereof, and lithium ion battery

Abstract

The application relates to the technical field of battery materials, and discloses a coated lithium-rich lithium supplement material, a preparation method and application thereof, and a lithium ion battery. The material comprises a matrix and a coating layer coated on the surface of the matrix; the matrix comprises Li2NiO2; the coating layer comprises a carbon-composite lithium-rich layer; the lithium-rich layer is selected from at least one of Li2CO3, Li2C2O4 and Li2C4O4; the mass ratio of the content of Li2NiO2, the lithium-rich layer and carbon elements in the coating layer is 100:1-5:0.1-2.5; and the average particle diameter of the coated lithium-rich lithium supplement material is 12-18 mu m. The coated lithium-rich lithium supplement material provided by the application has excellent air stability and lithium supplement capacity, and has the advantages of simple preparation process, high repeatability and easy large-scale promotion.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a coated lithium-rich lithium supplement material, its preparation method and application, and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries play an irreplaceable role in both the electric vehicle sector and large-scale grid energy storage. Further improving the energy density and cycle life of lithium-ion batteries can deepen the electrification transformation and the construction of new power systems. Li2NiO2 is a lithium-rich transition metal oxide that can release a large amount of active lithium during the first charge-discharge process to compensate for the active lithium loss caused by the SEI film, thereby effectively improving the energy density and cycle life of lithium-ion batteries.

[0003] The most suitable way to use Li2NiO2 on a large scale is to add it directly to the positive electrode slurry. This method does not require changes to the existing homogenization process, using Li2NiO2 as an additive. However, Li2NiO2 has poor structural stability in humid air, and Li2O precipitates on the surface, gradually reacting with moisture and CO2 in the air to form LiOH and Li2CO3. The presence of LiOH and Li2CO3 easily causes the slurry to gel, making the coating process difficult. In addition, the generated LiOH and Li2CO3 have poor conductivity, which also hinders the lithium replenishment capacity of Li2NiO2 and weakens its lithium replenishment effect. Furthermore, after Li2NiO2 decomposes during charging, it forms NiO, which remains in the battery without any positive effect.

[0004] Surface coating is one of the most effective methods to improve the air stability of Li₂NiO₂. Researchers have modified the surface of Li₂NiO₂ by coating it with carbon, hydrophobic substances, oxides, fast ion conductors, etc., but these substances are all non-electrochemically active and easily reduce the lithium replenishment capacity. Some studies have modified the surface of Li₂NiO₂ by coating it with Li₂Se, Li₃N, Li₆CoO₄, etc. Although these substances are electrochemically active, they are still sensitive to air and moisture and cannot effectively improve the air stability of Li₂NiO₂.

[0005] Therefore, finding a simple and suitable method to improve the air stability of Li2NiO2 without sacrificing its specific capacity is crucial for the further promotion and application of Li2NiO2.

[0006] CN115347254A discloses a composite cathode lithium supplement additive, comprising cathode lithium supplement material particles. The characteristic feature is that a lithium carbonate coating layer is further bonded to the surface of the cathode lithium supplement material particles. The lithium carbonate coating layer covers the cathode lithium supplement material particles, and the lithium carbonate is generated by the reaction of residual alkali contained in the cathode lithium supplement material particles. Although this solution achieves improved air stability by coating the lithium supplement agent with lithium carbonate, the lithium carbonate is only used as a coating layer and does not provide lithium supplement capacity. Furthermore, the residual substances after the decomposition of lithium-rich transition metal oxides are left unused.

[0007] CN111977703A discloses a method for preparing a Li2O / Li2CO3-coated transition metal sulfide-based cathode material. The method comprises: adding Li2S to anhydrous ethanol in a protective atmosphere according to a required amount, stirring and mixing to obtain a clear solution; adding transition metal sulfide-based material powder and multi-walled carbon nanotubes to the clear solution according to a required amount to form a mixed solution, and continuing to stir and heat the mixed solution until the anhydrous ethanol is completely evaporated to obtain Li2S / C-coated transition metal sulfide-based material powder; grinding the obtained powder evenly, placing it in air to allow partial or complete hydrolysis of Li2S to form LiOH; calcining the powder in an inert gas, and cooling it to obtain the Li2O / Li2CO3-coated transition metal sulfide-based cathode material. Although this scheme suppresses volume expansion, alleviates side reactions with the electrolyte, and prevents polysulfide shuttle by coating with Li2O and Li2CO3, the capacity of Li2O and Li2CO3 as lithium replenishing agents is not fully utilized. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of poor air stability, reduced specific capacity after surface modification, and poor electrochemical performance after application in batteries of existing surface-modified lithium supplements.

[0009] To achieve the above objectives, the first aspect of the present invention provides a coated lithium-rich lithium replenishing agent material, the material comprising a matrix and a coating layer coated on the surface of the matrix; the matrix comprising Li2NiO2; the coating layer comprising a carbon composite lithium-rich layer; the lithium-rich layer being selected from at least one of Li2CO3, Li2C2O4, and Li2C4O4;

[0010] The mass ratio of carbon content in the Li2NiO2, the lithium-rich layer, and the coating layer is 100:1-5:0.1-2.5;

[0011] The average particle diameter of the coated lithium-rich lithium supplement material is 12-18 μm.

[0012] A second aspect of the present invention provides a method for preparing the coated lithium-rich lithium supplement material described in the first aspect, the method comprising:

[0013] (1) In the presence of a solvent, the lithium source and the carbon source are first mixed to obtain a mixed solution;

[0014] (2) Mix Li2NiO2 with the mixed solution a second time to obtain a precursor solution;

[0015] (3) The precursor solution is dried to obtain the coated lithium-rich lithium supplement material;

[0016] The lithium source is selected from at least one of Li2CO3, Li2C2O4, and Li2C4O4;

[0017] The mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon, is 100:1-5:0.1-2.5.

[0018] The third aspect of the present invention provides a coated lithium-rich lithium supplement material prepared by the method described in the second aspect.

[0019] The fourth aspect of the present invention provides the application of the coated lithium-rich lithium replenishing agent materials described in the first and third aspects in the field of lithium-ion battery technology.

[0020] A fifth aspect of the present invention provides a lithium-ion battery comprising: a positive electrode, a separator, and a negative electrode; wherein the positive electrode is coated with a lithium replenishing agent material; wherein the lithium replenishing agent material is the coated lithium-rich lithium replenishing agent material described in the first and second aspects.

[0021] Compared with the prior art, the coated lithium-rich lithium supplement material provided by the present invention has the following beneficial effects:

[0022] (1) The preparation process is simple, highly reproducible, and easy to promote on a large scale;

[0023] (2) The coated lithium-rich lithium replenishing agent material provided by the present invention has excellent air stability;

[0024] (3) The coated lithium-rich lithium replenishing agent material provided by the present invention makes full use of the synergistic effect of the matrix material and the coating layer. The matrix material catalyzes the coating layer to help it decompose and obtain capacity. The coating layer improves the stability of the matrix material, freeing it from the problem of residual alkali, so that the lithium replenishing capacity can be fully utilized. Attached Figure Description

[0025] Figure 1 This is a graph showing the static contact angle test results of the material with water obtained by Example 1 and Comparative Example 2 provided by the present invention.

[0026] Figure 2 This is an electron microscope image of the material obtained in Embodiment 1 of the present invention. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] As previously described, a first aspect of the present invention provides a coated lithium-rich lithium replenishing agent material, the material comprising a matrix and a coating layer coated on the surface of the matrix; the matrix comprising Li2NiO2; the coating layer comprising a carbon composite lithium-rich layer; the lithium-rich layer being selected from at least one of Li2CO3, Li2C2O4, and Li2C4O4;

[0029] The mass ratio of carbon content in the Li2NiO2, the lithium-rich layer, and the coating layer is 100:1-5:0.1-2.5;

[0030] The average particle diameter of the coated lithium-rich lithium supplement material is 12-18 μm.

[0031] This invention, through inventive research, discovers that by introducing a carbon-composite lithium-rich layer onto the surface of Li2NiO2, and controlling the mass ratio of carbon elements in Li2NiO2, the lithium-rich layer, and the coating layer within the aforementioned specific range, a coated lithium-rich lithium replenishing agent material can simultaneously achieve excellent air stability and lithium replenishment capacity. The surface carbon is also a hydrophobic material, capable of blocking moisture and improving overall conductivity, thus aiding in lithium replenishment capacity. The lithium-rich layer itself is also a lithium replenishing agent, possessing a higher lithium replenishment capacity than Li2NiO2, but its high decomposition voltage hinders its ability to fully utilize its capacity. However, the NiO formed after the first charge of Li2NiO2 can act as a catalyst to effectively reduce the decomposition voltage of the lithium-rich layer, allowing it to achieve its lithium replenishment capacity. Furthermore, the surface-coated carbon also enhances the conductivity of the lithium-rich layer and reduces the decomposition voltage.

[0032] To better utilize the lithium replenishment capacity of the coating layer, the lithium-rich layer is preferably Li2CO3.

[0033] More preferably, the mass ratio of carbon content in the Li2NiO2, the lithium-rich layer, and the coating layer is 100:2-5:0.2-1. The inventors have found that, under this preferred embodiment, the coated lithium-rich lithium replenisher obtained by the present invention has a higher lithium replenishment capacity.

[0034] Preferably, the average particle diameter of the coated lithium-rich supplemental material is 12-16 μm.

[0035] As previously described, a second aspect of the present invention provides a method for preparing the coated lithium-rich lithium supplement material described in the first aspect, the method comprising:

[0036] (1) In the presence of a solvent, the lithium source and the carbon source are first mixed to obtain a mixed solution;

[0037] (2) Mix Li2NiO2 with the mixed solution a second time to obtain a precursor solution;

[0038] (3) The precursor solution is dried to obtain the coated lithium-rich lithium supplement material;

[0039] The lithium source is selected from at least one of Li2CO3, Li2C2O4, and Li2C4O4;

[0040] The mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon, is 100:1-5:0.1-2.5.

[0041] Preferably, the lithium source is Li2CO3.

[0042] More preferably, the mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon element, is 100:2-5:0.2-1.

[0043] Preferably, the carbon source is selected from at least one of carbon nanotubes, graphene, acetylene black, and Ketjen black.

[0044] More preferably, the carbon source is selected from carbon nanotube aqueous dispersions and / or graphene aqueous dispersions.

[0045] More preferably, the solid content of the carbon nanotube aqueous dispersion and the graphene aqueous dispersion are each independently 4-6 wt%. Through inventive research, this invention has discovered that this preferred embodiment helps to achieve uniform coating, and the resulting lithium-replenishing material has higher conductivity. It also helps to improve the overall conductivity and reduce the decomposition voltage of the lithium-rich layer, thereby increasing its lithium-replenishing capacity.

[0046] It should be noted that, in this invention, if the carbon source is selected from carbon nanotube aqueous dispersion and / or graphene aqueous dispersion, then in the step of preparing the coated lithium-rich lithium supplement, the amount of carbon source used is based on the solid content in the carbon nanotube aqueous dispersion and / or graphene aqueous dispersion. This will not be elaborated further here, and those skilled in the art should not understand it as a limitation of this invention.

[0047] Preferably, in step (1), the mass ratio of the lithium source to the solvent is 1:100-300. The lithium ion concentration determines the solid content of the precursor solution. Through inventive research, this invention has found that excessively low lithium ion concentrations lead to high water content, low evaporation efficiency, lengthy processes, and significantly reduced energy consumption, while excessively high concentrations result in high viscosity of the precursor solution, causing severe particle agglomeration after drying, which is detrimental to uniform coating. Therefore, this invention preferably uses a mass ratio of lithium source to solvent of 1:100-300.

[0048] Preferably, in step (1), the solvent is water.

[0049] In a preferred embodiment, in step (1), the first mixing is performed under ultrasonic conditions, which include: a time of 10-30 min, a temperature of 25-60 °C, and an ultrasonic frequency of 45-55 kHz.

[0050] Preferably, in step (2), the conditions for the second mixing include: a time of 30-120 min and a temperature of 25-60 °C.

[0051] More preferably, the second mixing is carried out under stirring conditions. The present invention does not have special requirements for the stirring speed, and it can be carried out in a conventional manner in the art. For example, the stirring speed can be 1000-2000 rpm.

[0052] Preferably, in step (3), the drying is carried out by spray drying, and the conditions for spray drying include: a feed rate of 100-2000 mL / h and an air inlet temperature of 120-220℃.

[0053] More preferably, the spray drying conditions include an inlet air temperature of 180-220°C. The inventors have found that, under this preferred embodiment, the lithium-containing solution evaporates faster without oxidizing the carbon, resulting in a more uniform coating of the coated lithium-rich supplemental agent obtained by this invention.

[0054] As previously described, a third aspect of the present invention provides a coated lithium-rich lithium replenishing agent material prepared by the method described in the second aspect.

[0055] As previously stated, the fourth aspect of the present invention provides the application of the coated lithium-rich lithium replenishing agent materials described in the first and third aspects in the field of lithium-ion battery technology.

[0056] As previously described, a fifth aspect of the present invention provides a lithium-ion battery comprising: a positive electrode, a separator, and a negative electrode; wherein the positive electrode is coated with a lithium replenishing agent material; wherein the lithium replenishing agent material is the coated lithium-rich lithium replenishing agent material described in the first and second aspects above.

[0057] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available products.

[0058] Example 1

[0059] This embodiment illustrates that the coated lithium-rich lithium supplement material provided by the present invention is prepared using the following steps:

[0060] Carbon source: 5 wt% carbon nanotube dispersion;

[0061] Lithium source: Li2CO3;

[0062] (1) 5g of Li2CO3 and 5wt% carbon nanotube dispersion were mixed with 500g of deionized water to obtain a mixed solution; the conditions for the first mixing were: ultrasonic frequency of 50kHz, time of 30min, and temperature of 25℃.

[0063] (2) The Li2NiO2 is mixed with the mixed solution for a second time to obtain a precursor solution; the conditions for the second mixing are: stirring speed of 1000 rpm, time of 30 min, and temperature of 25℃.

[0064] (3) The precursor solution is spray-dried to obtain the coated lithium-rich lithium supplement material S1; the conditions for spray drying are: feed rate of 800 mL / h; air inlet temperature of 200℃;

[0065] The mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon, is 100:5:1.

[0066] Example 2

[0067] Carbon source: 5 wt% carbon nanotube dispersion;

[0068] Lithium source: Li2C2O4;

[0069] (1) 5g of Li2C2O4 and 5wt% carbon nanotube dispersion were mixed with 500g of deionized water to obtain a mixed solution; the conditions for the first mixing were: ultrasonic frequency of 50kHz, time of 30min, and temperature of 25℃.

[0070] (2) The Li2NiO2 is mixed with the mixed solution for a second time to obtain a precursor solution; the conditions for the second mixing are: stirring speed of 1000 rpm, time of 30 min, and temperature of 25℃.

[0071] (3) The precursor solution is spray-dried to obtain the coated lithium-rich lithium supplement material S2; the conditions for spray drying are: feed rate of 800 mL / h; air inlet temperature of 200℃;

[0072] The mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon, is 100:5:1.

[0073] Example 3

[0074] Carbon source: 5 wt% carbon nanotube dispersion;

[0075] Lithium source: Li2C4O4;

[0076] (1) 5g of Li2C2O4 and 5wt% carbon nanotube dispersion were mixed with 500g of deionized water to obtain a mixed solution; the conditions for the first mixing were: ultrasonic frequency of 50kHz, time of 30min, and temperature of 25℃.

[0077] (2) The Li2NiO2 is mixed with the mixed solution for a second time to obtain a precursor solution; the conditions for the second mixing are: stirring speed of 1000 rpm, time of 30 min, and temperature of 25℃.

[0078] (3) The precursor solution is spray-dried to obtain the coated lithium-rich lithium supplement material S3; the conditions for spray drying are: feed rate of 800 mL / h; air inlet temperature of 200℃;

[0079] The mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon, is 100:5:1.

[0080] Example 4

[0081] This embodiment illustrates that the coated lithium-rich lithium supplement material provided by the present invention is prepared using the following steps:

[0082] Carbon source: 4 wt% carbon nanotube dispersion;

[0083] Lithium source: Li2CO3;

[0084] (1) 5g of Li2CO3 and 4wt% carbon nanotube dispersion were mixed with 500g of deionized water to obtain a mixed solution; the conditions for the first mixing were: ultrasonic frequency of 45kHz, time of 20min, and temperature of 25℃.

[0085] (2) The Li2NiO2 is mixed with the mixed solution for a second time to obtain a precursor solution; the conditions for the second mixing are: stirring speed of 1000 rpm, time of 120 min, and temperature of 25℃.

[0086] (3) The precursor solution is spray-dried to obtain the coated lithium-rich lithium supplement material S1; the conditions for spray drying are: feed rate of 800 mL / h; air inlet temperature of 180℃;

[0087] The mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon, is 100:2:0.2.

[0088] Example 5

[0089] This embodiment follows a similar process to Embodiment 1. The difference is that in this embodiment, the amount of Li2CO3 remains unchanged, but the mass ratio of Li2NiO2, Li2CO3 and carbon source, calculated as Li2NiO2, lithium source and carbon element respectively, is 100:5:2.

[0090] Everything else is the same as in Example 1.

[0091] The coated lithium-rich lithium supplement material S5 was prepared.

[0092] Example 6

[0093] This embodiment follows a similar process to Embodiment 1. The difference is that in this embodiment, the amount of Li2CO3 remains the same, but the mass ratio of Li2CO3 to deionized water is 1:90 (that is, the amount of deionized water is 450g).

[0094] Everything else is the same as in Example 1.

[0095] The coated lithium-rich lithium supplement material S6 was prepared.

[0096] Example 7

[0097] This embodiment follows a similar process to Example 1. The difference is that, in this embodiment, an equal mass of carbon nanotube dispersion with a concentration of 6.5 wt% is used to replace the 5 wt% carbon nanotubes in Example 1.

[0098] Everything else is the same as in Example 1.

[0099] The coated lithium-rich lithium supplement material S7 was prepared.

[0100] Example 8

[0101] This embodiment uses a similar process to that of Embodiment 1, except that the spray drying temperature is 150°C in this embodiment.

[0102] Everything else is the same as in Example 1.

[0103] The coated lithium-rich lithium supplement material S8 was prepared.

[0104] Comparative Example 1

[0105] This comparative example follows a similar process to Example 1. The difference is that the amount of Li2CO3 is kept constant, but the mass ratio of Li2NiO2, Li2CO3 and carbon source, calculated as Li2NiO2, lithium source and carbon element respectively, is 100:5.5:1.

[0106] Everything else is the same as in Example 1.

[0107] Material DS1 was prepared.

[0108] Comparative Example 2

[0109] This comparative example uses Li2NiO2 as a reference.

[0110] Comparative Example 3

[0111] This comparative example follows a similar process to Example 1, except that Li2NiO2 is not added. The specific preparation steps are as follows:

[0112] Carbon source: 5 wt% carbon nanotube dispersion;

[0113] Lithium source: Li2CO3;

[0114] (1) 5g of Li2CO3 and 5wt% carbon nanotube dispersion were mixed with 500g of deionized water to obtain a mixed solution; the conditions for the first mixing were: ultrasonic frequency of 50kHz, time of 30min, and temperature of 25℃.

[0115] (2) The mixed solution is spray-dried to obtain the material DS3; the conditions for spray drying are: feed rate of 800 mL / h; air inlet temperature of 200℃;

[0116] The mass ratio of the lithium source and the carbon source, calculated as Li2NiO2, lithium source and carbon element respectively, is 5:1.

[0117] Comparative Example 4

[0118] This comparative example follows a similar procedure to Example 1, except that no carbon source is added. The specific preparation steps are as follows:

[0119] (1) Mix 5g of Li2CO3 with 500g of deionized water to obtain a mixed solution; the conditions for the first mixing are: ultrasonic frequency of 50kHz, time of 30min, and temperature of 25℃.

[0120] (2) The Li2NiO2 is mixed with the mixed solution for a second time to obtain a precursor solution; the conditions for the second mixing are: stirring speed of 1000 rpm, time of 30 min, and temperature of 25℃.

[0121] (3) The precursor solution is spray-dried to obtain the material DS4; the conditions for spray drying are: feed rate of 800 mL / h; air inlet temperature of 200℃;

[0122] The mass ratio of Li2NiO2 to the lithium source is 100:5.

[0123] Comparative Example 5

[0124] This comparative example follows a similar process to Example 1, except that no lithium source is added. The specific preparation steps are as follows:

[0125] (1) 20g of carbon nanotube dispersion with a concentration of 5wt% was mixed with 500g of deionized water to obtain a mixed solution; the conditions for the first mixing were: ultrasonic frequency of 50kHz, time of 30min, and temperature of 25℃.

[0126] (2) The Li2NiO2 is mixed with the mixed solution for a second time to obtain a precursor solution; the conditions for the second mixing are: stirring speed of 1000 rpm, time of 30 min, and temperature of 25℃.

[0127] (3) The precursor solution is spray-dried to obtain the coated lithium-rich lithium supplement material S1; the conditions for spray drying are: feed rate of 800 mL / h; air inlet temperature of 200℃;

[0128] The mass ratio of Li2NiO2 and the carbon source, calculated as Li2NiO2 and carbon elements respectively, is 100:1.

[0129] The parameter characteristics of the materials prepared in the above examples are shown in Table 1.

[0130] Table 1

[0131]

[0132] The present invention also provides, by way of example, an electron microscope image of the coated lithium-rich lithium replenishing agent material obtained in Example 1 ( Figure 1As can be seen from the figure, Li2NiO2 is covered by a layer of fine particles. This is because the lithium salt dissolved in water is spray-dried and recrystallized to form nanoparticles that coat the surface, indicating that Li2NiO2 is successfully coated by a lithium-rich layer and a carbon layer.

[0133] Test Example 1

[0134] 0.08g of the material provided in the above example was mixed with 0.01g of acetylene black, 0.01g of polyvinylidene fluoride and 0.5mL of N-methylpyrrolidone to obtain a slurry. The slurry was coated on aluminum foil to form a positive electrode sheet. The positive electrode sheet, lithium metal sheet (negative electrode), separator and electrolyte were assembled into a CR2032 coin cell.

[0135] The charging capacity of the assembled battery was tested within a voltage range of 2.0-4.5V at a rate of 0.1C. The test results are shown in Table 2.

[0136] Table 2

[0137]

[0138] As can be seen from Table 2, the coated lithium-rich supplementary material provided by this invention can achieve better capacity. Among them, when the lithium source ratio is high, carbon and Li2NiO2 cannot sufficiently reduce their decomposition voltage, resulting in the lithium-rich layer being unable to achieve its capacity. However, when there is no lithium-rich layer and coating layer, Li2NiO2 is easily corroded by air during battery manufacturing, resulting in low specific capacity. When only lithium-rich layer and carbon are present, the specific capacity of the material is poor due to the lack of catalytic effect of Li2NiO2. When only Li2NiO2 and lithium-rich layer are present, the specific capacity is poor due to the lack of carbon to improve the conductivity of the lithium-rich layer. When no lithium-rich layer is present, the specific capacity of the material is poor due to the lack of surface lithium-rich layer capacity.

[0139] Test Example 2

[0140] This test example is used to exemplarily illustrate the air stability of the coated lithium-rich lithium replenishing agent material obtained by the present invention;

[0141] Test method: Contact angle meter. After tableting, water was used as the contact medium, and the static contact angle was measured using the seated drop method. Each sample was tested three times. The test results are shown below. Figure 2 .

[0142] from Figure 2 As can be seen, Comparative Example 2 has a smaller contact angle with water, while Example 1 has a larger contact angle with water, indicating that the carbon composite lithium-rich layer can effectively prevent Li2NiO2 from being corroded by moisture in the air.

[0143] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing coated lithium-rich lithium supplement materials, characterized in that, The method includes: (1) In the presence of a solvent, the lithium source and the carbon source are first mixed to obtain a mixed solution; (2) The Li2NiO2 is mixed with the mixed solution for a second time to obtain a precursor solution; (3) The precursor solution is dried to obtain the coated lithium-rich lithium supplement material; The lithium source is selected from at least one of Li2CO3, Li2C2O4, and Li2C4O4; The mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon, is 100:1-5:0.1-2.

5. The coated lithium-rich lithium replenishing agent material includes a matrix and a coating layer coated on the surface of the matrix; the matrix includes Li2NiO2; the coating layer includes a carbon composite lithium-rich layer; the lithium-rich layer is selected from at least one of Li2CO3, Li2C2O4, and Li2C4O4; The mass ratio of carbon content in the Li2NiO2, the lithium-rich layer, and the coating layer is 100:1-5:0.1-2.5; The average particle diameter of the coated lithium-rich lithium supplement material is 12-18 μm.

2. The method according to claim 1, characterized in that, The lithium-rich layer is Li2CO3; And / or, the mass ratio of carbon content in the Li2NiO2, the lithium-rich layer, and the coating layer is 100:2-5:0.2-1; And / or, the average particle diameter of the coated lithium-rich supplemental material is 12-16 μm.

3. The method according to claim 1, characterized in that, The lithium source is Li2CO3; And / or, the mass ratio of the Li2NiO2, the lithium source, and the carbon source, respectively, based on the amount of Li2NiO2, lithium source, and carbon element, is 100:2-5:0.2-1.

4. The method according to claim 1 or 2, characterized in that, The carbon source is selected from at least one of carbon nanotubes, graphene, acetylene black, and Ketjen black.

5. The method according to claim 4, characterized in that, The carbon source is selected from carbon nanotube aqueous dispersions and / or graphene aqueous dispersions.

6. The method according to claim 5, characterized in that, The solid content of the carbon nanotube aqueous dispersion and the graphene aqueous dispersion are each 4-6 wt%.

7. The method according to any one of claims 1-3, characterized in that, In step (1), the mass ratio of the lithium source to the solvent is 1:100-300.

8. The method according to any one of claims 1-3, characterized in that, In step (1), the first mixing is carried out under ultrasonic conditions, which include: time of 10-30 min, temperature of 25-60℃, and ultrasonic frequency of 45-55 kHz. And / or, in step (2), the conditions for the second mixing include: a time of 30-120 min and a temperature of 25-60 °C; And / or, in step (3), the drying is carried out by spray drying, and the conditions for spray drying include: a feed rate of 100-2000 mL / h and an air inlet temperature of 120-220℃.

9. The method according to claim 8, characterized in that, The conditions for spray drying include an inlet air temperature of 180-220℃.

10. A coated lithium-rich lithium supplement material prepared by the method according to any one of claims 1-8.

11. The application of the coated lithium-rich lithium replenishing agent material according to claim 10 in the field of lithium-ion battery technology.

12. A lithium-ion battery, characterized in that, The lithium-ion battery includes: a positive electrode, a separator, and a negative electrode; the positive electrode is coated with a lithium replenishing agent material; the lithium replenishing agent material is the coated lithium-rich lithium replenishing agent material as described in claim 10.

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